Secure your Facebook account | Change Password: Learning to secure your account should be important to you because it says so much about you, and you should be the only person who
has access to it. If someone gains access to your account, or creates
an
account to pretend to be you or someone else, Facebook's team could help
but you need to help yourself first.

If you think your account has been hacked, you should visit this link https://web.facebook.com/hacked to secure your account. From there, you'll be asked you to change your password and review recent login activity.

Click on "Security and Login" on the left hand side of the pop up page.

Under "Login" click on "Edit" at the right-hand of "Change password"

Fill in the "Current", "New" and "Retype New" fields. Current is your current password, New is the new password you want to change your current to and Retype New means you should retype that your new password.